Assessment of the superior photocatalytic properties of Sn 2+ -containing SnO 2 microrods on the photodegradation of methyl orange.

A microporous Sn 2+ -containing SnO 2 material presenting microrod morphology and a surface area of 93.0 m 2  g -1 was synthesized via a simple hydrothermal route. Sn 2+ ions were detected in the interior of the material (15.8 at.%) after the corrosion of a sample through sputtering. The material's optical properties have demonstrated the absorption of a considerable fraction of visible light up to wavelengths of 671 nm, due to the presence of Sn 2+ states in the material's band structure. The analysis of the internal crystalline structure of a single microrod was carried out with the aid of a focused ion beam microscope and indicated that the material is mesocrystalline down to nanoscale level. It was proposed that the Sn 2+ ions occupy intergranular sites in the highly defective crystalline structure of the material and that Sn 2+ states, as well as its relatively large surface area, are responsible for the material's superior photoactivity. The synthesized material was tested as a photocatalyst to decompose hazardous contaminants in water. The photocatalytic performance of the material was much higher than those of commercial TiO 2 and SnO 2 materials, decomposing nearly all methyl orange (an azo-dye model) content in water (10 mg L -1 ) in 6 min under UV irradiation for a photocatalyst dose of 5.33 g L -1 . The photodegradation of methyl orange was also verified under visible light.